The invention generally relates to wireless communication systems. In particular, the invention relates to data detection in a wireless communication system.
FIG. 1 is an illustration of a wireless communication system 10. The communication system 10 has base stations 121, to 125 (12) which communicate with user equipments (UEs) 141 to 143 (14). Each base station 12 has an associated operational area, where it communicates with UEs 14 in its operational area.
In some communication systems, such as frequency division duplex using code division multiple access (FDD/CDMA) and time division duplex using code division multiple access (TDD/CDMA), multiple communications are sent over the same frequency spectrum. These communications are differentiated by their channelization codes. To more efficiently use the frequency spectrum, TDD/CDMA communication systems use repeating frames divided into timeslots for communication. A communication sent in such a system will have one or multiple associated codes and timeslots assigned to it.
Since multiple communications may be sent in the same frequency spectrum and at the same time, a receiver in such a system must distinguish between the multiple communications. One approach to detecting such signals is multiuser detection (MUD). In MUD, signals associated with all the UEs 14, users, are detected simultaneously. Another approach to detecting a multi-code transmission from a single transmitter is single user detection (SUD). In SUD, to recover data from the multi-code transmission at the receiver, the received signal is passed through an equalization stage and despread using one or multiple codes. Approaches for implementing MUD and the equalization stage of SUD include using a Cholesky or an approximate Cholesky decomposition. These approaches have a high complexity. The high complexity leads to increased power consumption, which at the UE 14 results in reduced battery life. Accordingly, it is desirable to have alternate approaches to detecting received data.
K data signals are transmitted over a shared spectrum in a code division multiple access communication system. A combined signal is received and sampled over the shared spectrum. The combined signal has the K transmitted data signals. A combined channel response matrix is produced using the codes and impulse responses of the K transmitted data signals. A block column of a combined channel correlation matrix is determined using the combined channel response matrix. Each block entry of the block column is a K by K matrix. At each frequency point k, a K by K matrix xcex9(k) is determined by taking the fourier transform of the block entries of the block column. An inverse of xcex9(k) is multiplied to a result of the fourier transform. Alternately, forward and backward substitution can be used to solve the system. An inverse fourier transform is used to recover the data from the K data signals.